Method of producing supercalendered plasticized glassine paper



April 1953 G. c. BORDEN, JR 2,636,833

METHOD OF PRODUCING SUPERCALENDERED PLASTIGIZED GLASSINE PAPER Filed Nov. 7. 1952 2 SHEETS-SHEET l INVENTOR W a M f, BY I 4: M MMZZJQWPM ATTO R N EYS April 1953 G. c. BORDEN, JR 2,636,833

METHOD OF PRODUCING SUPERCALENDERED PLASTICIZED GLASSINE PAPER Filed NOV. 7. 1952 2 SHEETS-SHEET 2 FIG. 2

6 rmreo 572.551! Paper a INVT R ATTORNEYS Patented Apr. 28, 1953 METHOD OF PRODUClNG SUPERCALEN- DERED PLASTICIZED GLASSINE PAPER George C. Borden, Jr., Milford, N. J assignor to Riegel Paper Corporation, New York, N. Y., a corporation of New Jersey Application November 7, 1952, Serial No. 319,303

3 Claims.

. '1 This invention relates to improvements in the manufacture of supercalendered glassine paper and more particularly to the production of such paper with a high content of invert sugar as a plasticizer.

It has heretofore been proposed to improve the pliability of glassine paper by the addition of glycerine, hygroscopic salts and sugars to impart to the paper a desirable plasticity. See, for example, United States Patents Nos. 1,914,798; 2,058,961; 2,268,674 and 2,403,697.

' In the summertime, when the humidity becomes quite high, dlffifillltles are presented when highly hygroscopic substances such as glycerine, glycols and hygroscopic salts such as calcium chloride are used by the picking up of an excessive amount of moisture which causes the paper to become gray, soft, and very rag y, all of which are undesirable, as the transparency of the glassine is decreased, and articles wrapped therewith give the appearance of oldness and staleness of the wrapper.

' Invert sugars which do not hold such large quantities of moisture are more desirable as plasticizing agents during the summer months,

but their use in large amount tends to cause caramelization of the sugar which in turn tends to darken or yellow the glassine paper when subjected to supercalendering treatment. This takes place with or without the admixture of hygroscopic salts if the proportion of sugar is great enough. The supercalendered glassine paper is commonly rolled up into rolls where the paper tends to remain hot for a considerable period of time.

The temperature at which supercalender rolls are run varies between temperatures, e. g., around 270 to 300 F. to lower temperatures between 200 and 250 F. The speed at which the paper is run through the supercalendering rolls is around 450 feet to 1000 feet per minute. The time required for passing the paper through the supercalender is a small fraction of a minute and ;may be only a few seconds. But during this operation, the paper is compressed between the calender rolls and is heated by the rolls and, at the same time, it is cooled on one side, where it passes around the rolls, and on both sides in its travel between the rolls. The temperature of the paper is usually considerably below that of the heated rolls but may approach the temperature of these rolls. And the temperature of the paper may vary at different parts of the calender and at different portions of the width of the paper. The paper, or a part of the paper, may thus, during its travel through the supercalender, be

heated to temperatures above, and often considerably above, 160, and to temperatures as high as 185 or 200 F. or higher, but below that temperature which will injure the paper.

Where plasticized glassine papers of the character above referred to are subjected to supercalendering and leave th rolls and are rolled up into a paper roll, at temperatures above or materially above 160 F. there is a tendency to cause caramelization of the sugar and darkening or yellowing of the paper, and to some extent weakening and brittlizing of the product, with resulting rejection and loss of the paper.

I have found that there is a critical temperature below which danger of caramelization or yellowing of the supercalendered glassine paper is obviated, and that glassine paper plasticized with a high content of invert sugar can readily be produced and kept without danger of darkening by rapidly cooling the hot, supercalendered paper below the critical temperature as it leaves the supercalender and before it is Wound into a roll. This critical temperature is in the neighborhood of to R, which is a radically lower temperature than the high temperature of the supercalender rolls and also materially below the temperature to which the paper itself is heated during its passage through the supercalender. This temperature, as above indicated, is above and frequently very much above F.

The cooling of the supercalendered glassine paper from a temperature which would cause objectionable discoloration to below the critical temperature can be accomplished by blowing cold air against the paper as it passes from the supercalender to the wind-up roll or by passing the paper in contact with chilled rolls or by running the temperature of the last calender roll at a temperature which will accomplish the required reduction in temperature.

I have found that by blowing a strong current of cold air onto the paper as it leave the supercalender and before it is wound into a roll the temperature can be rapidly lowered and kept below about 140 F., and that color reversion does not take place in the paper so treated.

I have further found that by proceeding in this way I have been able, during the humid summer months, to use only invert sugars to plasticize the glassine papers without danger of darkening the color.

I The use of invert sugar alone in the summertime is advantageous, avoiding excessive water absorption and retention, while imparting a desirable degree of hy roscopicity and plasticityito the superc'alendered'glassine. Papers having a high degree of plasticity and containing in excess of of plasticizer can thus be prepared with the use of invert sugar alone as the plasticizer. Even with this high content of invert sugar danger of discoloration caused by caramelization wa readily obviated by promptly and rapidly cooling the supercalendered paper to a temperature below about 140 F.

In the case of glassine paper which is to be lacquered or waxed after supercalendering, I have used a solution containing up to invert sugar in treating the glassine paper on'the size press in the dryer train prior to supercalendering with a plastic retention in the paper of about 15% of the invert sugar. sugar makes the paper soft, with a good finish, and it does not pick up the excessive amounts This quantity of invertof moisture which glycerine and various hy roscopic salts such as calcium chloride, magnesium chloride or sodium nitrate would tend to pick up.

I have also found that during the winter months, under low humidity conditions, invert sugars retain the moisture within the sheet more tenaciously than glycerin and give up the moisture more slowly. However, under such conditions, glycerin and other such liquid plasticizers, such as ethylene and diethylene glycol, etc., have the added advantages that they will hold a greater quantity of moisture at the start of the drying out operation, so that there is more water to be lost, and that they do not crystallize but will remain liquid and in turn will prevent the sugars from crystallizing. It is accordingly advantageous during the winter months to use a small percentage of glycerin or other fluid, liquid plasticizers in conjunction with a high proportion of the invert type of sugars. Thus, in the wintertime, for glassine paper which is to be super-- calendered, a mixture of about 1 part of glycerin or glycerin-type plasticizer is advantageously used with about 2 parts of invert sugar.

The method of treating the glassine paper with the invert sugar, prior to supercalendering, may be that which has been heretofore described, for example, in the United States Patent to Bidwell No. 1,914,799, in which the invert sugar or mixture of invert sugar and glycerin-type plasticizer is applied in a size press, located at an intermediate stage of the dryer train. The plasticizing invert sugar solution can alsobe applied in part to the partially dried web of glassine paper on the dryers and in part after the paper is completely dried, as described in United States Patent No. 2,058,961.

The uncalendered and plasticized glassine paper, plasticized with a high content of invert sugar, is then subjected to supercalendering treatment by passing over supercalender rolls heated to a high temperature, around 270 to 300 F., and heated to temperatures during the supercalendering as high as 180 or 200 F., or higher so that the paper leaves the supercalender at temperatures materially above 160 F. After leaving the supercalendering rollsand before the supercalendered paper is rolled into a roll, the paper is rapidly and effectively cooled by a blast of cold air to a temperature below the critical temperature, around 1&0 to 150 F.

Arrangements of apparatus for treating the uncalendered paper to supercalender and cool it are shown in a somewhat conventional and diagrammatic manner in the accompanying drawings, in which Fig. 1 shows an arrangement-for cooling the paper with cold air after supercalendering and before rolling the paper into rolls; and

Fig. 2 shows an arrangement of supercalender rolls with provision for cooling the paper before it leaves the supercalender.

In the arrangement of apparatus, shown in Fig. 1, a roll of the: uncalendered plasticized glassine paper, plasticized with a high content of invert sugar, is supplied by the roll I and passed over the heated supercalender rolls 2. The hot supercalendered paper as indicated at 3 passes to the calendered'paper roll 4 and on its travel between the supercalender rolls and the paper roll it is subjected to a blast of cold air which passes over the cooling coils 5 and is blown by the fan 0 through the pipe 1 which has its discharge outlets directed against the bottom side of the paper-and also against the top side of the paper as it is being rolled on the roll. Such a blast of cold air rapidly cools, thehot supercalendered vglassinepaper below F, so that'the paper in the rollis kept well'below the critice1 temperature.

In the arrangement of apparatus illustratedin Fig. 2, the uncalendered and plasticized glassine paper, plasticized by the high content of invert sugar, is supplied by the roll [0. The supercalender is made up of an upper steel'roll' H, steam heatedrolls l2, paper rolls [3, guide rolls Hi, and'a lower roll provided'with cooling means :5, and witha guide roll 16 for the'paper going to the'Wind-up'roll H for'the calenderedglassine paper.

In this apparatus the uncalendered glassine paper from the roll- [0 passes over the top-roll it and-around guide rolls [4 and between the steam heated rolls l2 and the paper rolls l3, where it is subjected to supercalendering pressure and also heated=by the steam heatedrolls. The paper is cooled by the air in its passage around the guide rolls. With the steam heated rolls heated by steam at around 300 F'., the paper will be rapidly and momentarily heated during its passage between the-heated rolls and the paper rolls and may reach-temperatures around 180 or 200 F. or higher and, unless specially cooled, would-come ofi ofthe supercalender and goto the wind-up roll at temperatures above, and often materially above, F. By passing the'paper over the cooled roll I5, or by omitting steamfro'm the-lower'steam heated roll [2, or both, thepaper canbereadily and rapidly cooled to below 140F. before it pa'sses over the guide rolls 1% and is wound up on theroll l 1.

By such rapid cooling of the hot, supercalenderedpaper, it is possible, as above indicated, to produce-an improved plasticized supercalendered glassine paperof desirable pliability with a high content of invertsugar and with the use of such sugar aloneinthe summertime when humidity is high, and without danger of objectionable caramelization or colorreversion of the supercalendered'glassine paper.

Similarly, in the wintertime, under conditions of low-humidity, animprovedplasticized supercalendered glassine paper-canreadily be produced with a major proportion of invert sugar and a smaller proportion of liquid type glassine plasticizer as the=plasticizing material.

This application is a continuation-in-part: of my prior application Serial No; 110,567" filed August 16, 1949, now, abandoned.

I claim:

1. The method of producing plasticizedsupe'r calendered. glassine paper. which..comprise's ap- 5 plying to the glassine paper a plasticizing composition containing invert sugar as its principal plasticizing medium, supercalendering the plasticized glassine paper by passing it over heated rolls and heating the paper during supercalendering to a temperature above 160 E, which would cause caramelization or discolorization of the invert sugar if the supercalendered paper were permitted to cool slowly, the maximum temperature to which the paper is heated during the supercalendering being below that temperature at which the paper will be injured, rapidly cooling the paper after the supercalendering thereof to a temperature below about 140 F. so that caramelization or discolorization of the paper the plasticizing composition contains in addition to the invert sugar a compound from the class consisting of glycerine and the glycols.

GEORGE C. BORDEN, J R.

No references cited 

1. THE METHOD OF PRODUCING PLASTICIZED, SUPERCALENDERED GLASSINE PAPER WHICH COMPRISES APPLYING TO THE GLASSINE PAPER A PLASTICIZING COMPOSITION CONTAINING INVERT SUGAR AS ITS PRINCIPAL PLASTICIZING MEDIUM, SUPERCALENDERING THE PLASTICIZED GLASSINE PAPER BY PASSING IT OVER HEATED ROLLS AND HEATING THE PAPER DURING SUPERCALENDERING TO A TEMPERATURE ABOVE 160* F., WHICH WOULD CAUSE CARAMELIZATION OR DISCOLORIZATION OF THE INVERT SUGAR IF THE SUPERCALENDERED PAPER WERE PERMITTED TO COOL SLOWLY, THE MAXIMUM TEMPERATURE TO WHICH THE PAPER IS HEATED DURING THE SUPERCALENDERING BEING BELOW THAT TEMPERATURE AT WHICH THE PAPER WILL BE INJURED, RAPIDLY COOLING THE PAPER AFTER THE SUPERCALENDERING THEREOF TO A TEMPERATURE BELOW ABOUT 140* F. SO THAT CARAMELIZATION OR DISCOLORIZATION OF THE PAPER DOES NOT TAKE PLACE, AND THEREAFTER ROLLING THE COOLED SUPERCALENDERED GLASSINE PAPER IN A ROLL. 